1,721,000 research outputs found
Dynamics-induced surface metallization of Si(100)
No full textHigh-temperature surface metallization of Si(100) is observed at T > 900
K by high-resolution electron-energy-loss and ultraviolet photoemission
spectroscopy. Metallization takes place well below the incomplete
surface melting temperature and is consistent with the Si dimer
dynamics, characterized by an instantaneous symmetriclike dimer
configuration. The surface free carrier concentration in the metallic
phase has been evaluated, reaching (at 1170 K) the same order of
magnitude of the surface dimer density
Core-level photoemission study of 2D ordered Bi/Si(100) interfaces
No full textA high resolution fore-level photoemission investigation of 2D ordered
Bi layers grown on Si(100)-(2 x 1) is presented. We study the Si 2p and
Bi 5d core-levels at room temperature as a function of coverage and in
the reconstructed phases. The different Bi structural configurations
around the monolayer coverage and in the (2 x n)-reconstructed phase are
derived from the core-level lineshape evolution. By following the Fermi
level pinning, the presence of Bi-induced occupied electronic states
close to the Si mid-gap is suggested. (C) 1999 Elsevier Science B.V. All
rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Long range ordered pentacene chains assembled on Cu(119) vicinal surface
No full textPentacene (C22H14), deposited on the Cu(119) vicinal surface, forms ordered molecular chains, with the long molecular axis aligned along the step direction. Phase correlation between neighboring chains gives rise to large domains, observed in the low-energy electron-diffraction (LEED) pattern. Scanning tunneling microscopy (STM) images show that the molecules are laying flat on the copper terraces with the molecular axis aligned along the steps, hence, facing the short side of one another. High-resolution STM data suggest that the molecules adsorb, locating the central benzene ring on the hollow site of the Cu(001) surface
Fractal TiO2 Nanostructures by Nonthermal.Laser Ablation at Ambient Pressure
No full textFractal TiO2 nanostructures in crystalline form are obtained at ambient pressure and temperature by pulsed laser deposition with femtosecond pulses. The synthesized structures have been studied by scanning electron microscopy, Raman spectroscopy, and X-ray photoemission spectroscopy. We show that the dendritic aggregations deposited on silicon wafers at room temperature are fractals. They are composed by nanoparticles with an average diameter in a range below 20 nm, with the presence of larger nanoparticles with a diameter above 50 nm. We demonstrate that the fractal dimension and area can be tuned by varying laser fluence and sample/target distance. X-ray photoemission spectroscopy shows that the as-deposited nanostructures are TiO2 while Raman spectroscopy reveals that the crystalline structure of fractals and nanoparticles are composed either by rutile or anatase phase, with a dominant relative concentration of anatase. We discuss possible mechanism of fractals and nanoparticles formation in comparison with the literature results
Surface electronic structure at Si(100)-(2x1)
No full textThe surface electronic structure of the clean Si(100)-(2x1) surface at
room temperature is studied by high-resolution electron-energy-loss
spectroscopy. Main absorption edge is detected at similar to 0.4 eV,
which corresponds to the energy gap of the system, further structures
are singled out at 0.8 and 1.25 eV and ascribed to interband electronic
transitions between dimer-related levels. The paramount importance of
cleanness is addressed showing and quantifying the effect of the
residual gas atmosphere (that can be present in ultrahigh vacuum) on the
electronic structure
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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